20" iMac, Network Issues.. Not happy

Well.. I bit the bullet and bought one of those new 20" iMac Core Duo's that everyone raves about.. I'm a Network Engineer for PC Systems so I'm pretty up on technology and computers.. However this mac has me lost..

I recently got it, hooked it up.. Wireless Networking was perfect.. I run a Linksys WRT54G Ver. 6 that handles two PC's on hard line and 3 PC Laptops on Wireless.. The iMac was performing flawlessly. Not a single hiccup, I'm also using WEP 128bit Encryption. The other day I installed VMWare Fusion so I could run XP for little things the MAC couldn't do. About 4 hours later I lost wireless.. I tried everything.. It would say "Connection Timedout", "Incompatible Security", etc.. I pulled the security off wireless, then reactivated it.. All went well.. MAC went back to working until this morning.. It's doing it again..

None of my PC Wireless connected computers have a problem.. Is this a device driver issue with the iMac? Should I reinstall the OS? I really don't want to buy a new router because I don't think thats it.. If it was then all my wireless connections including both my iPhones would do it.. But they don't.. I'm completely lost and don't know what to do.. Any advice?